Computers For The Masses, Not The Classes

Retro is new again, and everywhere you look you’ll find films, documentaries, and TV shows cashing in on the nostalgia of their target audience. There is one inaccuracy you’ll find with this these shows: Apple computers are everywhere. This isn’t a historical truth – Commodore was everywhere, the C64 was the computer the nerds actually used, and to this day, the Commodore 64 is still the best-selling computer in history.

Commodore is gone, replaced with a superfund site, but the people who made the best computers in history are still around. At the 2016 Hackaday SuperConference, Bil Herd gave a talk on the second act of Commodore’s three-act tragedy. Bil is a frequent contributor around these parts, and as always he illuminates the 1980s far better than Halt and Catch Fire ever could.

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Compiling a $22 Logic Analyzer

On my way to this year’s Hackaday SuperConference I saw an article on EE Times about someone taking the $22 Lattice iCEstick and turning it into a logic analyzer complete with a Python app to display the waveforms. This jumped out as pretty cool to me given that there really isn’t a ton of RAM on the stick, basically none that isn’t contained in the FPGA itself.

[Jenny List] has also written about the this application as created by [Kevin Hubbard] of Black Mesa Labs and [Al Williams] has a great set of posts about using this same $22 evaluation board doing ground up Verilog design using open source tools. Even if you don’t end up using the stick as a logic analyzer over the long haul, it’ll be very easy to find many other projects where you can recompile to invent a new purpose for it.

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When Difference Matters: Differential Signaling

We have talked about a whole slew of logic and interconnect technologies including TTL, CMOS and assorted low voltage versions. All of these technologies have in common the fact that they are single-ended, i.e. the signal is measured as a “high” or “low” level above ground.

This is great for simple uses. But when you start talking about speed, distance, or both, the single ended solutions don’t look so good. To step in and carry the torch we have Differential Signalling. This is the “DS” in LVDS, just one of the common standards throughout industry. Let’s take a look at how differential signaling is different from single ended, and what that means for engineers and for users.

Single Ended

Collectively, standards like TTL, CMOS, and LVTTL are known as Single Ended technologies and they have in common some undesirable attributes, namely that ground noise directly affects the noise margin (the budget for how much noise is tolerable) as well as any induced noise measured to ground directly adds to the overall noise as well.

By making the voltage swing to greater voltages we can make the noise look smaller in proportion but at the expense of speed as it takes more time to make larger voltage swings, especially with the kind of capacitance and inductance we sometimes see.

Differential

diff4

Enter Differential Signaling where we use two conductor instead of one. A differential transmitter produces an inverted version of the signal and a non-inverted version and we measure the desired signal strictly between the two instead of to ground. Now ground noise doesn’t count (mostly) and noise induced onto both signal lines gets canceled as we only amplify the difference between the two, we do not amplify anything that is in common such as the noise.

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Blacksmith Forge Made From the Bathroom Sink

The sweltering heat had finally moved on and Giant Tick season was coming to a close (not kidding, they are HUGE here), when I decided to fire up my hacked together blacksmith forge made out of an old bathroom sink and aquarium stand.

In the age-old formula I needed to supply an air source to a fuel to create enough heat to make iron malleable. I got the idea that this particular bathroom sink might be a good candidate for a fire bowl after I banged my shin with it and then cursed at it. It was clearly made of cast iron and as proof it was clearly unfazed by my tirade of words which I hope my son has learned from the Internet and not from listening to me remodel the bathroom.

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From Gates to FPGA’s – Part 1: Basic Logic

It’s time to do a series on logic including things such as programmable logic, state machines, and the lesser known demons such as switching hazards. It is best to start at the beginning — but even experts will enjoy this refresher and might even learn a trick or two. I’ll start with logic symbols, alternate symbols, small Boolean truth tables and some oddball things that we can do with basic logic. The narrative version is found in the video, with a full reference laid out in the rest of this post.

Invert

1The most simple piece of logic is inversion; making a high change to low or a low change to high. Shown are a couple of ways to write an inversion including the ubiquitous “bubble” that we can apply almost anywhere to imply an inversion or a “True Low”. If it was a one it is now a zero, where it was a low it is now a high, and where it was true it is now untrue.

AND

2Moving on to the AND gate we see a simple truth table, also known as a Boolean Table, where it describes the function of “A AND B”. This is also our first opportunity to see the application of an alternate symbol. In this case a “low OR a low yields a low”

NAND

3Most if not all of the standard logic blocks come in an inverted form also such as the NAND gate shown here. The ability to invert logic functions is so useful in real life that I probably used at least three times the number of NAND gates as regular AND gates when doing medium or larger system design. The useful inversion can occur as spares or in line with the logic.

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Weekend Proves Hardware Wins Hackathons

Teams hacking on hardware won big this weekend in New York. There were ten teams that answered Hackaday’s call as we hosted the first ever hardware hackathon at the Tech Crunch Disrupt NYC. These teams were thrown into the mix with all of the software hackers TC was hosting and rose to the top. Eight out of our ten teams won!

As we suspected, having something physical to show off is a huge bonus compared to those showing apps and webpages alone. Recipe for awesome: Mix in the huge talent pool brought by the hardware hackers participating, then season with a dash of experience from mentors like [Kenji Larson], [Johngineer], [Bil Herd], [Chris Gammell], and many more.

Out of over 100 teams, first runner-up went to PicoRico, which built a data collection system for the suspension of a mountain bike. The Twillio prize went to Stove Top Sensor for Paranoid, Stubburn Older Parents which adds cellphone and web connectivity to the stove, letting you check if you remembered to turn off the burns. The charismatic duo of fifteen-year-olds [Kristopher] and [Ilan] stole the show with their demonstration of Follow Plants which gives your produce a social media presence which you can then follow.

We recorded video and got the gritty details from everyone building hardware during the 20-hour frenzy. We’ll be sharing those stories throughout the week so make sure to check back!

VCF East: [Bil Herd] And System Architecture

Last Friday the Vintage Computer Festival was filled up with more than a dozen talks, too many for any one person to attend. We did, however, check out [Bil Herd]’s talk on system architecture, or as he likes to call it, the art and science of performance through balance. That’s an hour and fifteen minute talk there; coffee and popcorn protocols apply.

The main focus of this talk is how to design a system from the ground up, without any assumed hardware, or any specific peripherals. It all starts out with a CPU, some memory (it doesn’t matter which type), and some I/O. That’s all you need, whether you’re designing a microwave oven or a supercomputer.

The CPU for a system can be anything from a 6502 for something simple, a vector processor for doing loads of math, or have a RISC, streaming, pipelined, SIMD architecture. This choice will influence the decision of what kind of memory to use, whether it’s static or dynamic, and whether it’s big or little endian. Yes, even [Bil] is still trying to wrap his head around endianness.

MMUs, I/O chips, teletypes, character displays like the 6845, and the ANTIC, VIC, and GTIA make the cut before [Bil] mentions putting the entire system together. It’s not just a matter of connecting address and data pins and seeing the entire system run. There’s interrupts, RTCs, bus arbitration, DTACK, RAS, and CAS to take care of that. That will take several more talks to cover, but you can see the one last Friday below.

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